var z = {
  _startForceLayoutIteration: function (forceLayout, layoutAnimation) {
    var self = this;
    (function step() {
      forceLayout.step(function (stopped) {
        self.updateLayout(self._model);
        (self._layouting = !stopped) && (
          layoutAnimation
            ? (self._layoutTimeout = setTimeout(step, 16))
            : step()
        );
      });
    })();
  }
};
